Maximum PC. LOL! :roll:
There was a time when it was cutting edge, but it's about 2-3 months behind the curve now, and far from an authority on Vista. I used to subscribe (all the way up to Dec'05), but cancelled once it was getting quite clear they were about 3-4 months behind HKEpc and The InQ for rumours and some fact, and they trailed all the major sites by 2-3 months for everything hardware related, especially if it was graphics, where new drivers or even new hardware made their articles obsolete by the time they hit the stands. Reading about the X1800/GF7800 when the X1900 is already in stores, or the GF7800 when the GF7900 and 7600 are making waves on the .net just doesn't make you want to renew your subscription for what used to be a KickAss mag, and now is only a 5 at best, heck CPU mag goes into more technical detail nowadays.
I suggest you read the Extremetech article at their site for a more recent view, and even then, we won't know the final number of version until Vista finally ships. I can see there being at least half a dozen, and if they do segment like they say they will and support 32 bit all the way to business server class in the consumer package, I'd suspect the total variations of Vista closer to double digits.
Even if very narrowed down for marketing for a focused push 3 version for the non-enterprise version alone seems a tight fit.
That would essentially make it 32 bit version, 64bit version low end 64bit high end, and even that's unlikely because I'd suspect they're going to have a media PC style version for people who want more than basic, but don't need hardcore networking or virtualization support.